The screw-incorporated barrel cylinder of an injection molding machine thus far used is heated with band type heaters installed respectively at the fore part (metering zone), intermediate part (compression zone) and rear part (feed zone) as disclosed in Japanese Patent Publication Laid-Open No. 55114-1990 while at the same time the heating temperatures at the respective zones are detected by a plurality of temperature sensors corresponding to said respective zones to perform temperature control with a controller. Further, the injection nozzle at the fore end of the barrel cylinder was also mounted with a temperature sensor for injection nozzle temperature control, and the hydraulic circuit had its oil temperature detected also with a temperature sensor. As temperature detection (temperature control) for the barrel cylinder, etc. is done in a high-temperature zone in this case, normally, thermostats are used as temperature sensors.
Incidentally, as shown in FIG. 2, of the present application, each of thermostats (temperature sensors) 3, . . . provided for injection unit M is branch connected in T-form, using a coupling cable such as RS-485 (trade name) with thermostat 3 serving as a master thermostat coupled to controller 2 having a computer function via data communication line 14 comprising an optical fibre cable, whereby injection unit temperature control system Ai undertaking temperature control for injection unit M is thus formed, wherein serial data communication is performed between controller 2 and each of individual thermostats 3, . . . according to a polling select system. Namely, in response to a call from controller 2, each of these thermostats 3, . . . is selected while each of detected values (numerical data) D.sub.3, D.sub.4, D.sub.5, D.sub.6 and D.sub.7 are transmitted sequentially therefrom to controller 2 and displayed on the display 15 of the controller 2. Also, command values S.sub.3, S.sub.4, S.sub.5, S.sub.6 and S.sub.7 of temperature designated by injection unit temperature selector 16 of controller 2 are transferred to respective thermostats 3, . . . and following these command values S.sub.2, . . . and detected values D.sub.2, . . . , control signals are subsequently fed to heaters 26, 27, 28, 29 installed respectively at, the metering zone (fore part), the compression zone (intermediate part) and the feed zone (rear part) of injection nozzle 21 and barrel cylinder 22, whereby feedback control of temperature is effected.
Meanwhile, temperature control of dies was carried out, using a die temperature regulator as disclosed in Japanese Patent Application Laid-Open No. 30725-1989. Presented in FIG. 2 of the present application is a die temperature control system Am provided with die temperature regulator 8. This die temperature control system Am runs with fluid, the temperature of which is regulated by die temperature regulator 8 supplied to circulated through) die 9, whereby die temperature control is performed.
In this case, die temperature regulator 8 is fed with command value Sm of die temperature designated by die temperature selector 17, to carry out feedback control of die temperature. Incidentally, similarly to the injection unit side, the die temperature control system Am is capable of remote control via a data communication line (refer to Japanese Utility Model Application Laid-Open No. 144617-1987).
However, because a conventional temperature control unit was constituted as comprising injection unit temperature control system Ai and die temperature control system Am being provided as separate control systems, the configuration of both hardware and software became complicated which resulted not only in a large increase of cost but also in deterioration of operability and maneuverability.
The reason why the conventional temperature control unit is constituted with separate control systems Ai and Am is described hereunder. Generally, because injection nozzle 21 and barrel cylinder 22 both have a function to melt molding material, the temperature of heating thereof is stabilized over a high-temperature range from 150.degree. through 400.degree. C. Therefore, it suffices that each of thermostats 3, . . . provided on the side off the injection unit is a thermostat capable of performing on/off-control each of heaters 26, . . . for the control of heating (heating only). On the other hand, the thermostat provided for dies 9 has respective functions to heat or cool the resin filled in a cavity within dies 9 and maintain the die temperature at a relatively low temperature range from 40.degree. through 100.degree. C. Accordingly, die temperature regulator 8 is required to function for not only heating to keep the die temperature at a setpoint but also for cooling to suppress the rise of die temperature due to the heat released from molten resin, whereby the thermostat used for die temperature control is required to perform dual control for heating and cooling. Meanwhile, when a heating/cooling dual control thermostat is compared with a heating control thermostat, the data related to setpoints and monitoring items and required for the former are almost twice as much similar data for the latter, regardless of conditions as to such control actions as (PID action, P action, PI action, etc. ) . Therefore, coupling the heating/cooling dual control thermostat and the heating control thermostat to controller 2 via a single data communication line results in a much more complex communication system and increase of cost than constituting with separate Ai and Am control systems.